Add plan capabilities to miniscript

Add a `plan` module that contains utilities to calculate the
cheapest spending path given an AssetProvider (that could
keys, preimages, or timelocks). Adds a `get_plan` method on the
various descriptor types.

Co-authored-by: Daniela Brozzoni <danielabrozzoni@protonmail.com>

Author: afilini

src/descriptor/bare.rs

@@ -24,8 +24,11 @@ use bitcoin::blockdata::script;
 use bitcoin::{Address, Network, Script};
 
 use super::checksum::{self, verify_checksum};
+use crate::descriptor::{DefiniteDescriptorKey, DescriptorType};
 use crate::expression::{self, FromTree};
 use crate::miniscript::context::ScriptContext;
+use crate::miniscript::satisfy::{Placeholder, WitnessTemplate};
+use crate::plan::{AssetProvider, Plan};
 use crate::policy::{semantic, Liftable};
 use crate::prelude::*;
 use crate::util::{varint_len, witness_to_scriptsig};
@@ -124,6 +127,28 @@ impl<Pk: MiniscriptKey + ToPublicKey> Bare<Pk> {
     }
 }
 
+impl Bare<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        self.ms
+            .build_template(provider)
+            .into_plan(DescriptorType::Bare)
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        self.ms
+            .build_template_mall(provider)
+            .into_plan(DescriptorType::Bare)
+    }
+}
+
 impl<Pk: MiniscriptKey> fmt::Debug for Bare<Pk> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}", self.ms)
@@ -278,6 +303,37 @@ impl<Pk: MiniscriptKey + ToPublicKey> Pkh<Pk> {
     }
 }
 
+impl Pkh<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        if provider.lookup_ecdsa_sig(&self.pk) {
+            let stack = vec![
+                Placeholder::EcdsaSigPk(self.pk.clone()),
+                Placeholder::Pubkey(self.pk.clone(), BareCtx::pk_len(&self.pk)),
+            ];
+            Some(Plan {
+                relative_timelock: None,
+                absolute_timelock: None,
+                desc_type: DescriptorType::Pkh,
+                template: WitnessTemplate::from_placeholder_stack(stack),
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        self.get_plan(provider)
+    }
+}
+
 impl<Pk: MiniscriptKey> fmt::Debug for Pkh<Pk> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "pkh({:?})", self.pk)

src/descriptor/key.rs

@@ -72,7 +72,7 @@ pub enum SinglePubKey {
 
 /// A [`DescriptorPublicKey`] without any wildcards.
 #[derive(Debug, Eq, PartialEq, Clone, Ord, PartialOrd, Hash)]
-pub struct DefiniteDescriptorKey(DescriptorPublicKey);
+pub struct DefiniteDescriptorKey(pub(super) DescriptorPublicKey);
 
 impl fmt::Display for DescriptorSecretKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -485,6 +485,27 @@ impl DescriptorPublicKey {
         DefiniteDescriptorKey::new(definite)
             .expect("The key should not contain any wildcards at this point")
     }
+
+    /// Whether this key matches a [`DefiniteDescriptorKey`]
+    ///
+    /// Returns `true` if this key is the un-derived version of the definite key passed in.
+    pub fn matches(&self, definite_key: &DefiniteDescriptorKey) -> bool {
+        // If the key is `Single` or it's an `XPub` with no wildcard it will match the definite key
+        // exactly, so we try this check first
+        if self == &definite_key.0 {
+            return true;
+        }
+
+        match (self, &definite_key.0) {
+            (DescriptorPublicKey::XPub(self_xkey), DescriptorPublicKey::XPub(definite_xkey)) => {
+                self_xkey.origin == definite_xkey.origin
+                    && self_xkey.xkey == definite_xkey.xkey
+                    && self_xkey.derivation_path.as_ref()
+                        == &definite_xkey.derivation_path[..(self_xkey.derivation_path.len() - 1)]
+            }
+            _ => false,
+        }
+    }
 }
 
 impl FromStr for DescriptorSecretKey {

src/descriptor/mod.rs

@@ -35,6 +35,7 @@ use sync::Arc;
 
 use self::checksum::verify_checksum;
 use crate::miniscript::{Legacy, Miniscript, Segwitv0};
+use crate::plan::{AssetProvider, Plan};
 use crate::prelude::*;
 use crate::{
     expression, hash256, miniscript, BareCtx, Error, ForEachKey, MiniscriptKey, Satisfier,
@@ -435,7 +436,7 @@ impl<Pk: MiniscriptKey + ToPublicKey> Descriptor<Pk> {
             Descriptor::Wpkh(ref wpkh) => wpkh.get_satisfaction(satisfier),
             Descriptor::Wsh(ref wsh) => wsh.get_satisfaction(satisfier),
             Descriptor::Sh(ref sh) => sh.get_satisfaction(satisfier),
-            Descriptor::Tr(ref tr) => tr.get_satisfaction(satisfier),
+            Descriptor::Tr(ref tr) => tr.get_satisfaction(&satisfier),
         }
     }
 
@@ -452,7 +453,7 @@ impl<Pk: MiniscriptKey + ToPublicKey> Descriptor<Pk> {
             Descriptor::Wpkh(ref wpkh) => wpkh.get_satisfaction_mall(satisfier),
             Descriptor::Wsh(ref wsh) => wsh.get_satisfaction_mall(satisfier),
             Descriptor::Sh(ref sh) => sh.get_satisfaction_mall(satisfier),
-            Descriptor::Tr(ref tr) => tr.get_satisfaction_mall(satisfier),
+            Descriptor::Tr(ref tr) => tr.get_satisfaction_mall(&satisfier),
         }
     }
 
@@ -470,6 +471,38 @@ impl<Pk: MiniscriptKey + ToPublicKey> Descriptor<Pk> {
     }
 }
 
+impl Descriptor<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match *self {
+            Descriptor::Bare(ref bare) => bare.get_plan(provider),
+            Descriptor::Pkh(ref pkh) => pkh.get_plan(provider),
+            Descriptor::Wpkh(ref wpkh) => wpkh.get_plan(provider),
+            Descriptor::Wsh(ref wsh) => wsh.get_plan(provider),
+            Descriptor::Sh(ref sh) => sh.get_plan(provider),
+            Descriptor::Tr(ref tr) => tr.get_plan(provider),
+        }
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match *self {
+            Descriptor::Bare(ref bare) => bare.get_plan_mall(provider),
+            Descriptor::Pkh(ref pkh) => pkh.get_plan_mall(provider),
+            Descriptor::Wpkh(ref wpkh) => wpkh.get_plan_mall(provider),
+            Descriptor::Wsh(ref wsh) => wsh.get_plan_mall(provider),
+            Descriptor::Sh(ref sh) => sh.get_plan_mall(provider),
+            Descriptor::Tr(ref tr) => tr.get_plan_mall(provider),
+        }
+    }
+}
+
 impl<P, Q> TranslatePk<P, Q> for Descriptor<P>
 where
     P: MiniscriptKey,

src/descriptor/segwitv0.rs

@@ -22,8 +22,11 @@ use bitcoin::{self, Address, Network, Script};
 
 use super::checksum::{self, verify_checksum};
 use super::SortedMultiVec;
+use crate::descriptor::{DefiniteDescriptorKey, DescriptorType};
 use crate::expression::{self, FromTree};
 use crate::miniscript::context::{ScriptContext, ScriptContextError};
+use crate::miniscript::satisfy::{Placeholder, WitnessTemplate};
+use crate::plan::{AssetProvider, Plan};
 use crate::policy::{semantic, Liftable};
 use crate::prelude::*;
 use crate::util::varint_len;
@@ -173,6 +176,32 @@ impl<Pk: MiniscriptKey + ToPublicKey> Wsh<Pk> {
     }
 }
 
+impl Wsh<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match &self.inner {
+            WshInner::SortedMulti(sm) => sm.build_template(provider).into_plan(DescriptorType::Wsh),
+            WshInner::Ms(ms) => ms.build_template(provider).into_plan(DescriptorType::Wsh),
+        }
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match &self.inner {
+            WshInner::SortedMulti(sm) => sm.build_template(provider).into_plan(DescriptorType::Wsh),
+            WshInner::Ms(ms) => ms
+                .build_template_mall(provider)
+                .into_plan(DescriptorType::Wsh),
+        }
+    }
+}
+
 /// Wsh Inner
 #[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
 pub enum WshInner<Pk: MiniscriptKey> {
@@ -393,6 +422,37 @@ impl<Pk: MiniscriptKey + ToPublicKey> Wpkh<Pk> {
     }
 }
 
+impl Wpkh<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        if provider.lookup_ecdsa_sig(&self.pk) {
+            let stack = vec![
+                Placeholder::EcdsaSigPk(self.pk.clone()),
+                Placeholder::Pubkey(self.pk.clone(), Segwitv0::pk_len(&self.pk)),
+            ];
+            Some(Plan {
+                relative_timelock: None,
+                absolute_timelock: None,
+                desc_type: DescriptorType::Wpkh,
+                template: WitnessTemplate::from_placeholder_stack(stack),
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        self.get_plan(provider)
+    }
+}
+
 impl<Pk: MiniscriptKey> fmt::Debug for Wpkh<Pk> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "wpkh({:?})", self.pk)

src/descriptor/sh.rs

@@ -25,8 +25,10 @@ use bitcoin::{Address, Network, Script};
 
 use super::checksum::{self, verify_checksum};
 use super::{SortedMultiVec, Wpkh, Wsh};
+use crate::descriptor::{DefiniteDescriptorKey, DescriptorType};
 use crate::expression::{self, FromTree};
 use crate::miniscript::context::ScriptContext;
+use crate::plan::{AssetProvider, Plan};
 use crate::policy::{semantic, Liftable};
 use crate::prelude::*;
 use crate::util::{varint_len, witness_to_scriptsig};
@@ -377,6 +379,44 @@ impl<Pk: MiniscriptKey + ToPublicKey> Sh<Pk> {
     }
 }
 
+impl Sh<DefiniteDescriptorKey> {
+    /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
+    pub fn get_plan<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match &self.inner {
+            ShInner::Wsh(ref wsh) => wsh.get_plan(provider).map(|mut plan| {
+                plan.desc_type = DescriptorType::ShWsh;
+                plan
+            }),
+            ShInner::Wpkh(ref wpkh) => wpkh.get_plan(provider).map(|mut plan| {
+                plan.desc_type = DescriptorType::ShWpkh;
+                plan
+            }),
+            ShInner::SortedMulti(ref _smv) => todo!(),
+            ShInner::Ms(ref ms) => ms.build_template(provider).into_plan(DescriptorType::Sh),
+        }
+    }
+
+    /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
+    pub fn get_plan_mall<P>(&self, provider: &P) -> Option<Plan>
+    where
+        P: AssetProvider<DefiniteDescriptorKey>,
+    {
+        match &self.inner {
+            ShInner::Wsh(ref wsh) => wsh.get_plan_mall(provider).map(|mut plan| {
+                plan.desc_type = DescriptorType::ShWsh;
+                plan
+            }),
+            ShInner::Ms(ref ms) => ms
+                .build_template_mall(provider)
+                .into_plan(DescriptorType::Sh),
+            _ => self.get_plan(provider),
+        }
+    }
+}
+
 impl<Pk: MiniscriptKey> ForEachKey<Pk> for Sh<Pk> {
     fn for_each_key<'a, F: FnMut(&'a Pk) -> bool>(&'a self, pred: F) -> bool
     where

src/descriptor/sortedmulti.rs

@@ -25,6 +25,8 @@ use bitcoin::blockdata::script;
 use crate::miniscript::context::ScriptContext;
 use crate::miniscript::decode::Terminal;
 use crate::miniscript::limits::MAX_PUBKEYS_PER_MULTISIG;
+use crate::miniscript::satisfy::{Placeholder, Satisfaction};
+use crate::plan::AssetProvider;
 use crate::prelude::*;
 use crate::{
     errstr, expression, miniscript, policy, script_num_size, Error, ForEachKey, Miniscript,
@@ -171,6 +173,16 @@ impl<Pk: MiniscriptKey, Ctx: ScriptContext> SortedMultiVec<Pk, Ctx> {
         ms.satisfy(satisfier)
     }
 
+    /// Attempt to produce a witness template given the assets available
+    pub fn build_template<P>(&self, provider: &P) -> Satisfaction<Placeholder<Pk>>
+    where
+        Pk: ToPublicKey,
+        P: AssetProvider<Pk>,
+    {
+        let ms = Miniscript::from_ast(self.sorted_node()).expect("Multi node typecheck");
+        ms.build_template(provider)
+    }
+
     /// Size, in bytes of the script-pubkey. If this Miniscript is used outside
     /// of segwit (e.g. in a bare or P2SH descriptor), this quantity should be
     /// multiplied by 4 to compute the weight.